Oriented strand board, parallel strand lumber and other engineered wood products produced from discrete wood elements are produced in a press by depositing a mat of resin coated wood elements within the press and applying a compressive force to the mat. Heat from a variety of sources is added to substantially cure the resin while the mat is within the press. The heat may be added in the form of microwave energy, radio frequency energy, steam injection or the like.
As depicted in FIG. 1, current press systems includes a pair of opposed platens 40a configured to continuously compress a material 38a into a desired shape. Adjacent each platen 40a is a press belt 37 running on roller or ball bearing arrangement 35. The belt 37 and bearing 35 combination allows movement of the material 38a through the platens 40a while the platens are continuously applying a compressive force to the material 38a. This method of forming a composite wood product is problematic in many ways.
The current continuous press designs impede the application of energy. The press belt, bearing arrangements and necessary lubrication materials represent a significant barrier for the application of heating energy to the product. The heating of the product via a hot platen technology results into an uneven heating profile which in turn yields an uneven density profile throughout the product.
The constant pressure applied also occasionally adversely affects the resulting product. The mat is generally an arrangement of wood elements formed in layers. When pressure is applied, often times there are pockets of air or moisture that gets trapped within the wood layers. As energy is applied, the natural moisture of the wood can form steam pockets in the regions of the trapped air. Subsequently, a blowout or other product defects result, thereby rendering the product unfit for its intended purpose.
Still further, the energy required to pull the material through current press systems is considerable. The constant pressure exerted by these press systems requires significant additional energy to move the material through the press system. The excessive amount of additional energy increases the cost of production thereby ultimately affecting market price for the product.